A research review has found that eating at least two handfuls of nuts a day may improve sperm quality – and, therefore, fertility – in young, healthy males. This simple strategy had positive effects without requiring any other changes to diet.
Infertility can have a huge impact on couples, causing emotional stress, depression, anxiety, and low self-esteem. With infertility on the rise, more and more research is focused on identifying modifiable lifestyle factors that affect fertility, such as diet.
Led by researchers at Monash University, a new, first-of-its-kind meta-analysis and review of human studies has found that eating nuts may improve sperm quality and, therefore, fertility in men.
“In the studies we reviewed, men were only required to consume 60-75 grams of nuts each day in order to achieve significant improvements in sperm quality,” said Nicole Kellow, one of the study’s corresponding authors. “This is only approximately two handfuls of nuts per day.”
The researchers included four studies involving 875 participants (646 men, 229 women) in their review. Two of the studies were observational; the other two, both randomized controlled trials (RCTs), were included in the meta-analysis.
The two RCTs collectively involved 223 healthy men in a similar age range – 18 to 35 – who reported eating a typical Western-style diet. One trial had participants eat 75 g of whole, shelled English walnuts a day for 12 weeks; the other provided 60 g (two handfuls) of a mixture of 30 g of walnuts, 15 g of almonds and 15 g of hazelnuts to their experimental group for 14 weeks. In both studies, the control group consumed a regular diet without nuts. The studies found that consuming at least two handfuls of nuts daily as part of a Western diet improved markers of sperm quality such as vitality, motility and morphology, but did not improve sperm concentration.
“The statistical analysis in both studies was adjusted for other factors such as physical activity,” said Barbara Cardoso, lead author of the study. “The findings show that this simple strategy has positive effects regardless of other lifestyles.”
The researchers say that apart from adding nuts, no other change was made to the participants’ diet.
“The trial participants ate a Western-style diet, which was not necessarily healthy,” Cardoso said. “This means that adding nuts to their regular diet had a positive effect without the need for further dietary changes.”
The non-randomized studies, involving participants with varied fertility status (e.g., low and normal sperm counts), reported no association between nut consumption and sperm quality.
The researchers suggest that the high concentration of omega-3 polyunsaturated fats, dietary fibers, vitamins, minerals and polyphenols found in nuts could improve reproductive health. While specific nuts were consumed in the studies reviewed by the researchers, they say that other types of nuts would likely also provide benefits.
“Many people think that nuts are fattening, but research shows that people who eat 1-2 handfuls each day are actually more likely to be leaner than those who don’t eat nuts,” Kellow said. “Also, nuts contain monounsaturated fats, antioxidants and dietary fiber, essential nutrients which are vital for good health.”
However, not all nuts are created equal, the researchers warn.
“We’re speaking of either raw or roasted nuts,” said Cardoso. “I’d avoid salted or sweetened nuts as sugar and can be associated with different health issues such as hypertension and insulin resistance.”
The researchers could find only two intervention studies examining the effect of nut consumption on male fertility and none relating to female fertility.
“The implications of these findings are of great value to people trying to conceive, but we also need to assess the effects of nuts on female fertility,” Cardoso said. “We would advocate for more male and female studies to strengthen the results.”
The study was published in the journal Advances in Nutrition.
Source: Monash University
